A range of probes is available for measuring intracellular ROS levels. Many are selective for H2O2, a relatively long-lived molecule to which the shorter-lived superoxide (O2–•) dismutes. Some can be targeted to the mitochondria or other cellular compartments. Ratiometric probes provide a signal that is independent of probe concentration. In vivo measurement is possible with some probes, including those that are genetically encoded.
Woolley et al 2013, Trends Biochem Sci
Some examples of ROS probes include:
1. MitoB/MitoP: H2O2 specific, targeted to mitochondria, ratiometric; measured with liquid chromatography–tandem mass spectrometry
Logan et al 2014, Biochimica et Biophysica Acta
2. PN1 and SHP-Mito: H2O2 specific, targeted to mitochondria (SHP-Mito), ratiometric; measured with fluorescence microscopy
Masanta et al 2012, Chem Commun
3. roGFP2-Orp1 transgenic D. melanogaster: redox-sensitive GFP coupled to microbial H2O2 sensor; expressed in cytosol or mitochondria; ratiometric; measured with fluorescence microscopy
Albrecht et al 2011, Cell Metabolism
4. HyPer transgenic C. elegans, D. rerio: redox-sensitive YFP coupled to microbial H2O2 sensor; expressed in cytosol or mitochondria; ratiometric; sensitive to pH changes; measured with fluorescence microscopy
Belousov et al 2006, Nature Methods; see also Bilan et al 2013, ACS Chem Biol
Other probes measure not the ROS concentration itself, but rather the damage that ROS inflicts on various cellular components. Examples include the reagent BODIPY 581/591 C11 for measuring lipid peroxidation; lipofuscin abundance as a measure of protein oxidation; and 8-oxo-2-deoxyguanosine (oxo8dG) as a measure of DNA oxidation.